Turbine blade turbulator cooling design

ABSTRACT

A turbine blade ( 10 ) includes internal channels ( 16 ) which provide a flow passage for a cooling medium to assist in cooling the blade ( 10 ) when in use, wherein the channels ( 16 ) include a plurality of turbulence promoting ribs ( 28, 60, 64, 70 ) mounted on the wall surfaces ( 44, 62, 66, 72 ) thereof. Each rib ( 28, 60, 64, 70 ) comprises two rib portions ( 30, 32 ) joined at one end to form a chevron junction ( 34 ), wherein the chevron junction ( 34 ) defines an angle ( 36 ) of between 80° and 120° and is directed into the flow of the cooling medium through the channels ( 16 ). Each rib portion ( 30, 32 ) of a rib ( 28, 60, 64, 70 ) defines a gap ( 40, 42 ) therein.

The present invention relates to turbomachinery, and in particular, butnot exclusively, to turbine blades for use in gas turbine engines.

Gas turbine engines are used in a number of applications, includingaircraft propulsion systems and power generation systems and the like.Typical gas turbine engines generally consists of three components: acompressor, a combustion chamber, and a turbine unit, wherein thecompressor and the turbine unit are mounted on the same shaft. In use,air is compressed by the compressor, is fed into the combustion chamberwhere it is mixed with fuel and the mixture is ignited, and the exhaustgases produced are then expanded through the turbine unit to drive theshaft and produce shaft work. In power generation applications, theshaft work produced is used to drive the compressor and turn electricalgenerators, often via a gearing system.

Conventional turbine units comprise a plurality of stages, each stageusually consisting of two sets of blades arranged in an annulus, thefirst set being stator or nozzle blades which are rotationally fixedwith respect to the casing of the turbine, and the second set beingrotor blades which are mounted on the shaft and rotate therewith. Thenumber of stages in a turbine unit is selected in accordance with, forexample, considerations of stage mechanical loading and thermodynamicperformance. Additionally, the number of stages may be determined by therequired pressure ratio from turbine inlet to outlet.

Turbine efficiency is an important factor in the design of any gasturbine engine and one method of increasing the performancecharacteristics involves maximising the temperature of the gas at theturbine inlet. However, increasing the temperature of the gas used todrive the turbine produces serious mechanical and thermal stressingproblems in the turbine blades, and the temperature of the gas islimited by the physical properties of the blade material, such asmelting point and yield strength and the like.

Various advancements in materials have been made for use in highpressure and temperature turbines, however, these are extremely costlydue to the complex formation process, for example, such asuni-directional crystallisation.

It is therefore common practice to minimise the thermal stress bycooling the blades during operation by passing cooling air bled from thecompressor externally and internally of the blades, such that higheroperational temperatures may be achieved, and the service life span ofthe blades may be increased. A number of blade designs exist which allowa particular cooling air flow regime to be utilised to allow acombination of, for example, convection cooling, impingement cooling andfilm cooling in order to improve the heat transfer properties betweenthe blade and the cooling air. However, the actual shape or design of ablade is often determined by a compromise between aerodynamic andintegrity requirements. Cooling primarily affects the integrityconsiderations both in terms of controlling the thermal stresses andmaintaining the operating temperature of the material within acceptablelimits to minimise creep and corrosion.

It is among the objects of the present invention to provide a turbineblade having improved cooling.

According to a first aspect of the present invention, there is provideda turbine blade having opposing pressure and suction side wallsadjoining at leading and trailing edges of the blade, and defining atleast one internal channel providing a flow passage for a coolingmedium, said at least one channel including a plurality of turbulencepromoting ribs mounted on a channel wall surface, wherein each ribcomprises two rib portions joined at one end thereof to form a chevronjunction, said chevron junction defining an angle of between 80° and120° between the two rib portions and being directed into the flow ofthe cooling medium within the at least one channel, and wherein each ribdefines at least one gap therein.

Thus, the turbine blade provides for improved heat transfer between theblade and the cooling medium due to the presence and form of the ribswithin the at least one channel.

Preferably, one rib portion is disposed at an angle of 120° from theother rib portion, i.e. the chevron junction angle between the ribportions is preferably 120°.

In a preferred embodiment of the present invention, the at least onechannel has a substantially triangular cross-section. The at least onechannel may alternatively have a substantially circular cross-sectionalshape, or any cross-sectional shape as would be considered suitable by aperson of ordinary skill in the art.

Preferably, adjacent ribs are aligned such that adjacent chevronjunctions are longitudinally aligned with respect to the at least onechannel. Alternatively, adjacent ribs may be misaligned such thatadjacent chevron junctions are longitudinally offset.

Advantageously, the ribs may be mounted on opposing sides of the atleast one channel, and each opposing rib may be laterally aligned withrespect to the at least one channel. Alternatively, the ribs may belaterally offset.

Preferably, the at least one gap of each adjacent rib are longitudinallyaligned with respect to the at least one channel. Alternatively, the atleast one gap in each adjacent rib may be longitudinally offset.

In a one embodiment of the present invention, each rib may define atleast two gaps. Preferably, at least one gap is provided in one ribportion, and at least one gap is provided in the other rib portion.

Preferably, the centre of each gap in each rib portion is locatedapproximately between 60% and 70%, and preferably around two thirds,along the length of each rib portion from the chevron junction.

Conveniently, at least one of the ribs may extend substantiallyperpendicular from the surface of the at least one channel.Alternatively, or additionally, at least one of the ribs may extend fromthe surface of the at least one channel at a non-perpendicular angle.Preferably, at least one of the ribs may extend from the surface of theat least one channel at an angle of between 45° to 135° with respect tothe direction of flow through the at least one channel. More preferably,the at least one rib extends at an angle of between 60° to 90°. Mostpreferably, the at least one rib extends at an angle of between 62° to79°. Thus, in a preferred embodiment of the present invention, at leastone rib extends from the surface of the at least one channel and isdirected into the direction of flow through the at least one channel.

Advantageously, the ribs may have a square cross-section. Alternatively,the ribs may have a cross-section in the form of a generalparallelogram. Alternatively further, the ribs may have a trapezoidalcross-section.

Advantageously, adjacent ribs are spaced apart by between 4 and 6 mm,and more preferably by between 4 and 5 mm. Most preferably, adjacentribs are spaced apart by 4.4 mm. It should be noted that the spacingbetween each rib is commonly referred to as the pitch.

Preferably, the ribs have a height of between 0.45 and 0.75 mm. Morepreferably, the ribs have a height of between 0.5 and 0.6 mm. Mostpreferably, the ribs have a height of 0.52 mm.

Advantageously, the ribs may have a width of between 0.45 and 0.75 mm.Preferably, the ribs have a width of 0.6 mm.

Conveniently, the width of the gaps in the ribs may be in the range of0.45 to 0.75 mm. In a preferred embodiment, the gaps in the ribs are0.54 mm wide.

Preferably, the at least one channel is located in the region of theleading edge. This arrangement is particularly advantageous as the atleast one channel including the ribs having the chevron junction givesgreatly enhanced cooling of the leading edge region where thermaldegradation of the blade most commonly occurs. Advantageously, the atleast one channel in the region of the leading edge is defined by thepressure wall, the suction wall and a web portion extending between thepressure and suction walls.

Preferably, when the ribs are located in at least one channel in theregion of the leading edge, one rib portion is located on the pressurewall, and the other rib portion is located on the suction wall, and thechevron junction is aligned with the leading edge.

Alternatively, the at least one channel may be located in a mid-passageof the blade, between the leading and trailing edges.

The blade may include a plurality of internal channels, at least one ofwhich channels being located in the region of the leading edge, and atleast one channel being located in a mid-passage of the blade, betweenthe leading and trailing edges.

Conveniently, the at least one channel may be of a single pass form.Alternatively, the at least one channel may be of a serpentine form, ora combination of single pass and serpentine forms may be utilised.

Conveniently, the turbine blade may further include a root portion and atip portion, wherein the pressure and suction walls and the leading andtrailing edges extend from the root portion to the tip portion of theblade.

Preferably, the cooling medium is supplied to the blade via the rootportion.

Preferably also, the root portion is of a fir-tree type. Alternatively,the root portion may be of a dove tail type, or any other type commonlyused in the art.

Advantageously, the external surface of the turbine blade may define aplurality of apertures providing fluid communication between the atleast one cooling channel and the exterior of the blade. Thus, coolingair internal of the blade may pass through the apertures to provide filmcooling to the exterior surface of the blade.

Conveniently, the cooling medium may be air, and preferably compressedair fed from a compressor.

Advantageously, the turbine blade may be for use in a gas turbineengine.

Preferably, the turbine blade is a rotor blade. Alternatively, theturbine blade may be a stator or nozzle blade.

More preferably, the turbine blade is a first stage rotor blade.

According to a second aspect of the present invention, there is provideda gas turbine engine including a plurality of turbine blades, at leastone turbine blade having opposing pressure and suction side wallsadjoining at leading and trailing edges of the blade, and defining atleast one internal channel providing a flow passage for a coolingmedium, said at least one channel including a plurality of turbulencepromoting ribs mounted on a channel wall surface, wherein each ribcomprises two rib portions joined at one end thereof to form a chevronjunction, said chevron junction defining an angle of between 80° and120° between the two rib portions and being directed into the flow ofthe cooling medium within the at least one channel, and wherein each ribdefines at least one gap therein.

According to a third aspect of the present invention, there is providedelectrical generating means including a gas turbine engine, said gasturbine engine including a plurality of turbine blades, at least oneturbine blade having opposing pressure and suction side walls adjoiningat leading and trailing edges of the blade, and defining at least oneinternal channel providing a flow passage for a cooling medium, said atleast one channel including a plurality of turbulence promoting ribsmounted on a channel wall surface, wherein each rib comprises two ribportions joined at one end thereof to form a chevron junction, saidchevron junction defining an angle of between 80° and 120° between thetwo rib portions and being directed into the flow of the cooling mediumwithin the at least one channel, and wherein each rib defines at leastone gap therein.

According to a fourth aspect of the present invention, there is provideda turbine blade having opposing pressure and suction side wallsadjoining at leading and trailing edges of the blade, and defining atleast one internal channel providing a flow passage for a coolingmedium, said at least one channel including a plurality of turbulencepromoting ribs mounted on a channel wall surface, wherein at least onerib has a trapezoidal cross-sectional shape and extends from the channelwall surface at an angle greater than 60° and less than 90°, such thatsaid at least one rib is directed into the flow of the cooling mediumwithin the at least one channel.

Preferably, the at least one rib extends from the channel wall surfaceat an angle of between 62° and 79°.

Preferably also, the cross-sectional shape of the at least one rib isdefined by a base and a tip joined by two flanks aligned parallel toeach other.

According to a fifth aspect of the present invention, there is provideda turbine blade having opposing pressure and suction side wallsadjoining at leading and trailing edges of the blade, and defining atleast one internal channel providing a flow passage for a coolingmedium, said at least one channel including a plurality of turbulencepromoting ribs mounted on a channel wall surface, wherein at least onerib has a cross-sectional shape in the form of a parallelogram andextends from the channel wall surface at an angle greater than 60° andless than 90°, such that said at least one rib is directed into the flowof the cooling medium within the at least one channel.

Preferably, at least one rib extends from the channel wall surface at anangle of between 62° and 79°.

Conveniently, various features defined above in accordance with thefirst aspect of the present invention may be applied to the second tofifth aspects, but for the purposes of brevity such features have notbeen repeated.

These and other aspects of the present invention will now be described,by way of example only, with reference to the accompanying drawings, inwhich:

FIG. 1 is a longitudinal cross-sectional view of a turbine blade inaccordance with one embodiment of the present invention;

FIG. 2 is a longitudinal cross-sectional view of an internal channel ofthe turbine blade of FIG. 1;

FIG. 3 is a perspective diagrammatic view of the channel shown in FIG.2;

FIGS. 4 to 6 are diagrammatic representations of the form of coolingribs according to various embodiments of the present invention; and

FIGS. 7 to 9 are partial schematic views of various embodiments of thepresent invention.

Reference is first made to FIG. 1 of the drawings in which there isshown a cross-sectional view of a turbine blade, generally indicated byreference numeral 10, for use in a gas turbine engine in accordance withone embodiment of the present invention. The blade 10 is a first stagerotor blade and has opposing pressure and suction side walls adjoiningat a leading edge 12 and a trailing edge 14 of the blade 10. The turbineblade 10 defines a number of internal channels 16, which channelsprovide a flow passage for a cooling medium, such as compressed air, tocool the blade 10 while in use. The blade also includes a root portion18 and a tip portion 20, wherein the cooling medium is supplied to theinternal channels 16 through the root portion 18. As shown, the rootportion 18 is of a fir-tree type.

The internal channels 16 consist of a leading edge channel 22 and anumber of mid-passage channels 24 located between the leading andtrailing edges 12, 14 of the blade 10. The leading edge channel 22 issubstantially triangular in cross-section and is a single pass channelaligned substantially parallel to the leading edge 12, wherein coolingair enters from the root portion 18, flows through the leading edgechannel 22, and exits the blade through an aperture 21 in the tipportion 20 of the blade 10. The mid-passage channels 24 on the otherhand are of a serpentine form, and provide a convoluted flow path forthe cooling medium or air. Air flowing through the mid-passage channels24 may exit the interior of the blade via apertures providing fluidcommunication between the channels 24 and the exterior of the blade,such as apertures 26 in the region of the trailing edge 14 of theturbine blade 10 or an aperture 23 in the tip portion 20 of the blade10.

In the embodiment shown, the leading edge channel 22 includes aplurality of upstanding turbulence promoting ribs which seek to improvethe heat transfer between the surfaces of the blade 10 and the coolingmedium. The ribs 28 are shown in FIG. 2 in which there is shown anenlarged longitudinal cross-sectional view of the leading edge channel22 of the turbine blade 10 of FIG. 1.

Each rib 28 comprises first and second rib portions 30, 32, whichportions 30, 32 join at one end to form a chevron junction 34, whereinthe arrangement is such that the first rib portion 30 is disposed at anangle 36 of around 120° from the second rib portion 32. The chevronjunction 34 of each rib is directed into the flow of the cooling medium,the flow direction being indicated in FIG. 2 by arrow 38. Additionally,the chevron junctions 34 of each adjacent rib 28 are longitudinallyaligned with respect to the channel flow direction 38.

Referring still to FIG. 2, each rib includes two gaps 40, 42 to furtherincrease the turbulence in the flow of cooling medium, wherein the gaps40, 42 of each rib 28 are longitudinally aligned with respect to thechannel 22.

In the embodiment shown, adjacent ribs 28 are separated from each other,i.e. the rib pitch, by around 4.4 mm and extend from the surface 44 ofthe channel 22 by a height of approximately 0.52 mm. Additionally, theribs 28 are approximately 0.6 mm wide, and the gaps 40, 42 in the ribs28 are approximately 0.54 mm wide.

Furthermore, the centre of each gap 40, 42 in each rib 28 is locatedapproximately two thirds along the length of each rib portion 30, 32respectively from the chevron junction 34.

Reference is now made to FIG. 3 of the drawings in which a perspectivediagrammatic view of the channel 22 is illustrated. As shown, thechannel 22 is triangular in cross-section and includes a plurality ofribs 28, each comprising first and second rib portions 30,32, whichportions 30,32 join at one end to form a chevron junction 34. Thechevron junctions 34 are directed into the direction of flow 38 ofcooling medium, and each junction 34 is aligned with the leading edge 12of the blade 10.

In the embodiment shown, the first rib portion 30 is mounted on thesuction wall 50, and the second rib portion 32 is mounted on thepressure wall 52.

As noted before, each rib includes two gaps 40, 42 which arelongitudinally aligned with respect to the channel 22.

Reference is now made to FIGS. 4 to 6 of the drawings in which there isshown diagrammatic representations of the form of a cooling rib inaccordance with different embodiments of the present invention.Referring initially to FIG. 4, there is shown a general form of a rib 60that extends substantially perpendicular from the surface 62 of acooling channel of a gas turbine blade.

Referring now to FIG. 5, a rib 64 defining a general parallelogramcross-sectional shape is shown. The rib 64 extends from the surface 66of a cooling channel at an angle A of between 62° to 79° such that therib 64 is directed into the flow direction of a cooling fluid, indicatedby arrow 68. A similar arrangement to that of FIG. 5 is shown in FIG. 6.In this embodiment, a rib 70 defines a trapezoidal cross-sectional shapeand extends from the surface 72 of a cooling channel at an angle A, asdefined above, of between 62° to 79°. The cross-sectional shape of rib70 is defined by a base 76, tip 78 and two flanks 80, 82, wherein theflanks 80, 82 are aligned parallel to each other. The rib 70 in FIG. 6defines an angle B of approximately 90°. Thus as with the embodimentshown in FIG. 5, rib 70 of FIG. 6 is directed into the cooling flowdirection, indicated by arrow 75. Directing the ribs 64, 70 into thedirection of flow in this manner increases the turbulence created in theflow, and thus increases the heat transfer between the ribs 64, 70 andthe cooling air. Additionally, directing the ribs in the mannerdescribed above with reference to FIGS. 5 and 6 allows the ribs to beformed with greater ease during the manufacturing process, particularlywhere the ribs are to be formed on the pressure and suction walls of theblade.

It should be obvious to a person of skill in the art that the abovedescribed embodiments are merely exemplary of the present invention andthat various modifications may be made thereto without departing fromthe scope of the present invention. For example, the chevron junction 34may define any suitable angle between first and second rib portions 30,32, and may be directed in line with the flow of cooling medium.Additionally, any number of gaps may be provided in the ribs, and thegaps of each adjacent rib may be offset or staggered. Furthermore, therib pitch may vary or be selected as required and is not necessarilyrestricted to the value given above. Similarly, the height and width ofeach rib, and the width of the gaps in each rib may vary.

The ribs of the turbine blade of the present invention have been shownin the accompanying representations in the leading edge channel 22.However, the particular form of ribs described herein may be used withinthe mid-passage channels 24, either in addition to or in place of thosein the leading edge channel.

Various further alternative embodiments will be described with referenceto FIGS. 7 to 9. Referring initially to FIG. 7, the cooling channel 22(FIG. 1) is shown which includes a plurality of cooling ribs 28 a whichare similar to cooling ribs 28 shown in FIG. 2 and as such each includea chevron junction 34 a and gaps 40 a, 42 a. In this embodiment thechevron junctions 34 a and gaps 40 a, 42 a of adjacent ribs 28 a arelongitudinally offset.

Referring to FIG. 8, an intermediate cooling channel 24 (FIG. 1) isshown in longitudinal cross section such that the opposing suction andpressure side walls 50, 52 may be identified. In this embodiment ribs 28b are provided on each wall 50, 52 and are arranged such that opposingribs 28 b are laterally aligned with respect to the channel 24. Analternative arrangement is shown in FIG. 9 in which opposing ribs 28 care laterally misaligned with respect to the channel.

1. A turbine blade having opposing pressure and suction side wallsadjoining at leading and trailing edges of the blade, and defining atleast one internal channel providing a flow passage for a coolingmedium, said at least one channel including a plurality of turbulencepromoting ribs mounted on a channel wall surface, at least one of theribs extending at an angle of between 62° and 79° from the surface ofthe at least one channel with respect to the direction of flowtherethrough, wherein each rib comprises two rib portions joined at oneend thereof to form a chevron junction, said chevron junction definingan angle of between 80° and 120° between the two rib portions and beingdirected into the flow of the cooling medium within the at least onechannel, and wherein at least one gap is provided in one rib portion,and at least one gap is provided in the other rib portion.
 2. A turbineblade as claimed in claim 1, wherein one rib portion is disposed at anangle of 120° from the other rib portion.
 3. A turbine blade as claimedin claim 1, wherein the at least one channel has a substantiallytriangular cross-section.
 4. A turbine blade as claimed in claim 1,wherein adjacent ribs are aligned such that adjacent chevron junctionsare longitudinally aligned with respect to the at least one channel. 5.A turbine blade as claimed in claim 1, wherein adjacent ribs aremisaligned such that adjacent chevron junctions are longitudinallyoffset.
 6. A turbine blade as claimed in claim 1, wherein the ribs aremounted on opposing sides of the at least one channel.
 7. A turbineblade as claimed in claim 6, wherein each opposing rib is laterallyaligned with respect to the at least one channel.
 8. A turbine blade asclaimed in claim 6, wherein each opposing rib is laterally offset withrespect to the at least one channel.
 9. A turbine blade as claimed inclaim 1, wherein the gaps of each adjacent rib are longitudinallyaligned with respect to the at least one channel.
 10. A turbine blade asclaimed in claim 1, wherein the gaps in each adjacent rib arelongitudinally offset with respect to the at least one channel.
 11. Aturbine blade as claimed in claim 1, wherein the centre of the at leastone gap is located between 60% and 70% along the length of a respectiverib portion from the chevron junction.
 12. A turbine blade as claimed inclaim 1, wherein the centre of the at least one gap is located aroundtwo thirds along the length of a respective rib portion from the chevronjunction.
 13. A turbine blade as claimed in claim 1, wherein at leastone of the ribs extends substantially perpendicular from the surface ofthe at least one channel.
 14. A turbine blade as claimed in claim 1,wherein the ribs have a trapezoidal cross-section.
 15. A turbine bladeas claimed in claim 1, wherein the ribs have a cross-section in the formof a parallelogram.
 16. A turbine blade as claimed in claim 1, whereinthe ribs have a square cross-section.
 17. A turbine blade as claimed inclaim 1, wherein adjacent ribs are spaced apart by between 4 and 5 mm.18. A turbine blade as claimed in claim 1, wherein adjacent ribs arespaced apart by between 4 and 5 mm.
 19. A turbine blade as claimed inclaim 1, wherein adjacent ribs are spaced apart by 4.4 mm.
 20. A turbineblade as claimed in claim 1, wherein the ribs have a height of between0.45 and 0.75 mm.
 21. A turbine blade as claimed in claim 1, wherein theribs have a height of between 0.5 and 0.6 mm.
 22. A turbine blade asclaimed in claim 1, wherein the ribs have a height of 0.52 mm.
 23. Aturbine blade as claimed in claim 1, wherein the ribs have a width ofbetween 0.45 and 0.75 mm.
 24. A turbine blade as claimed in claim 1,wherein the ribs have a width of 0.6 mm.
 25. A turbine blade as claimedin claim 1, wherein the gaps in the ribs are between 0.45 and 0.7.5 mmwide.
 26. A turbine blade as claimed in claim 1, wherein the gaps in theribs are 0.54 mm wide.
 27. A turbine blade as claimed in claim 1,wherein the at least one channel is located in the region of the leadingedge of the blade.
 28. A turbine blade as claimed in claim 1, whereinthe at least one channel is defined by the pressure wall, the suctionwall and a web portion extending between the pressure and suction walls.29. A turbine blade as claimed in claim 1, wherein the ribs are locatedin at least one channel in the region of the leading edge of the blade,such that one rib portion is located on the pressure wall, and the otherrib portion is located on the suction wall, and the chevron junction isaligned with the leading edge.
 30. A turbine blade as claimed in claim1, wherein the at least one channel is located in a mid-passage of theblade, between the leading and trailing edges of the blade.
 31. Aturbine blade as claimed in claim 1, wherein the blade includes aplurality of internal channels.
 32. A turbine blade as claimed in claim31, wherein at least one of the plurality of channels is located in theregion of the leading edge of the blade, and at least one channel islocated in a mid-passage of the blade, between the leading and trailingedges.
 33. A turbine blade as claimed in claim 1, wherein the at leastone channel is of a single pass form.
 34. A turbine blade as claimed inclaim 1, wherein the at least one channel is of a serpentine form.
 35. Aturbine blade as claimed in claim 1, wherein the turbine blade furtherincludes a root portion and a tip portion, wherein the pressure andsuction walls and the leading and trailing edges extend from the rootportion to the tip portion of the blade.
 36. A turbine blade as claimedin claim 35, wherein the cooling medium is supplied to the blade via theroot portion.
 37. A turbine blade as claimed in claim 35, wherein theroot portion is of a fir-tree type.
 38. A turbine blade as claimed inclaim 35, wherein the root portion is of a dove tail type.
 39. A turbineblade as claimed in claim 1, wherein the external surface of the turbineblade defines a plurality of apertures providing fluid communicationbetween the at least one cooling channel and the exterior of the blade.40. A turbine blade as claimed in claim 1, wherein the cooling medium isair.
 41. A turbine blade as claimed in claim 1, wherein the coolingmedium is compressed air fed from a compressor.
 42. A turbine blade asclaimed in claim 1, wherein the turbine blade is a rotor blade of a gasturbine engine.
 43. A turbine blade as claimed in claim 1, wherein theblade is a first stage rotor blade of a gas turbine engine.
 44. A gasturbine engine including a plurality of turbine blades, at least oneturbine blade having opposing pressure and suction side walls adjoiningat leading and trailing edges of the blade, and defining at least oneinternal channel providing a flow passage for a cooling medium, said atleast one channel including a plurality of turbulence promoting ribsmounted on a channel wall surface, at least one of the ribs extending atan angle of between 62° and 79° from the surface of the at least onechannel with respect to the direction of flow therethrough, wherein eachrib comprises two rib portions joined at one end thereof to form achevron junction, said chevron junction defining an angle of between 80°and 120° between the two rib portions and being directed into the flowof the cooling medium within the at least one channel, and wherein atleast one gap is provided in one rib portion, and at least one gap isprovided in the other rib portion.
 45. Electrical generating meansincluding a gas turbine engine, said gas turbine engine including aplurality of turbine blades, at least one turbine blade having opposingpressure and suction side walls adjoining at leading and trailing edgesof the blade, and defining at least one internal channel providing aflow passage for a cooling medium, said at least one channel including aplurality of turbulence promoting ribs mounted on a channel wallsurface, at least one of the ribs extending at an angle of between 62°and 79° from the surface of the at least one channel with respect to thedirection of flow therethrough, wherein each rib comprises two ribportions joined at one end thereof to form a chevron junction, saidchevron junction defining an angle of between 80° and 120° between thetwo rib portions and being directed into the flow of the cooling mediumwithin the at Least one channel, and wherein at least one gap isprovided in one rib portion, and at least one gap is provided in theother rib portion.
 46. A turbine blade having opposing pressure andsuction side walls adjoining at leading and trailing edges of the blade,and defining at least one internal channel providing a flow passage fora cooling medium, said at least one channel including a plurality ofturbulence promoting ribs mounted on a channel wall surface, wherein atleast one rib has a trapezoidal cross-sectional shape and extends fromthe channel wall surface at an angle greater than 60° and less than 90°,such that said at least one rib is directed into the direction of flowof the cooling medium within the at least one channel.
 47. A turbineblade as defined in claim 46, wherein the at least one rib extends fromthe channel wall surface at an angle of between 62° and 79°.
 48. Aturbine blade as defined in claim 46, wherein the cross-sectional shapeof the at least one rib is defined by a base and a tip joined by twoflanks aligned parallel to each other.
 49. A turbine blade havingopposing pressure and suction side walls adjoining at leading andtrailing edges of the blade, and defining at least one internal channelproviding a flow passage for a cooling medium, said at least one channelincluding a plurality of turbulence promoting ribs mounted on a channelwall surface, wherein at least one rib has a cross-sectional shape inthe form of a parallelogram and extends from the channel wall surface atan angle greater than 60° and less than 90°, such that said at least onerib is directed into the direction of flow of the cooling medium withinthe at least one channel.
 50. A turbine blade as defined in claim 49,wherein the at least one rib extends from the channel wall surface at anangle of between 62° and 79°.